The prevalence and severity of the milder forms of fluorosis in children is of concern in areas with optimal and above-optimal fluoride concentrations in community water supplies, and in instances of early supply of fluoride or known fluoride supplementation in an optimally fluoridated community. Mechanisms of fluorosis and the particular levels of fluoride in extracellular fluid associated with fluorosis are not well known. The proposed study will examine the clinical problem of fluorosis, using controlled fluoride levels, in an in vitro system where the delivery of fluoride to the ameloblasts of the enamel organ can be closely controlled. The effects of fluoride toxicity on the enamel organ will be studied using unerupted maxillary third molars of 12 day old rats grown as explants in organ culture in media containing various levels of fluoride. The study has two aims: (1) To develop a system in which the effect of fluoride on the enamel organ can be studied with closely controlled levels of fluoride and in which the enamel organ and dental papilla (with odontoblasts) can be separated for examination and analysis; and (2) To examine the effect of various levels of fluoride on amelogenesis vs. dentinogenesis, both histologically and assaying for mineral deposition and enzymes possibly related to mineralization and total protein synthesis. Following growth for up to 10 days in organ culture, the enamel organ and dental papilla will be separated by microdissection following trypsin digestion and the tissues analyzed. Organ cultures grown for 10 days will be radiolabeled with 45Ca and (3H) leucine in the final 24 hours of culture. This study constitutes an initial attempt to reproduce and measure the effects of fluoride on the rate of metabolic processes, using a simple system in which enamel formation is known to occur and in which fluoride concentrations can be precisely controlled. The study is preliminary in nature, and will consist to some extent in the adaptation of existing methods of separating enamel organ and dental papilla. Successful fulfillment of the above aims will allow the collection of data which will form the basis of a larger grant application, focusing particularly on the role of fluoride in synthesis of specific enamel proteins and mineral deposition.